Digital-to-analog converters convert a digital input codeword to an output analog signal, such as an output analog voltage or an output analog current. Interpolating string digital-to-analog converters include a coarse string digital-to-analog converter (DAC) circuit to generate high and low analog signals defining a coarse analog signal range based on a most-significant-bit (MSB) portion of the digital input codeword. Interpolating string DACs further include an interpolator circuit to interpolate, based on a least-significant-bit (LSB) portion of the digital input codeword, an analog signal having a value between the high and low analog signals defining the coarse analog signal range. This interpolated analog signal forms the overall analog signal to be output by the interpolating string DAC in response to the digital input codeword being applied to the input of the DAC.
The output analog signals generated by DACs, including interpolating string DACs, may exhibit nonlinearity errors, such as integral nonlinearity errors, differential nonlinearity errors, etc. To compensate for such errors, some DACs, including some interpolating string DACs, include a calibration DAC circuit to adjust the analog signal output by main DAC circuit. In general, the calibration DAC circuit is able to generate respective calibration signals for different digital input codewords, with the respective calibration signals being tailored to compensate for the particular nonlinearity errors exhibited by the respective analog signals generated by the main DAC circuit for the different digital input codewords. A calibration procedure is used to determine the respective calibration signals to be generated by the calibration DAC circuit for the different possible digital input codewords.